Berberine enhances the anti-HCC effect of NK cells through inhibiting interferon-gamma-mediated PD-L1 expression

Abstract Berberine (BBR) is an isoquinoline alkaloid with various functions in anti-inflammation, blocking tumor immune escape and enhancing the anti-tumor activity of immune cells. However, its immunomodulatory effect on natural killer (NK) cell activity in Hepatocellular carcinoma (HCC) is still unclear. Here, we determined whether BBR enhances the anti-HCC effect of NK cells and its mechanism by focusing on the regulation of the Programmed death-ligand 1 (PD-L1) pathway. It was found that BBR enhanced the cytotoxicity of NK92-MI cells to HCC cells in vitro and in vivo. The combination of BBR and PBMCs inhibited the proliferation and induced the apoptosis of HCC cells. BBR increased the frequency of CD3−CD56+ and CD3−CD16+ NK cells in peripheral blood isolated from healthy volunteers. Furthermore, the expression of PD-L1 in HCC cells was up-regulated after co-culture with NK-92MI cells or PBMCs. PD-L1 knockdown increased the sensitivity of HCC cells to NK-92MI cells and PBMCs. Mechanisms for BBR blocked the secretion of Interferon Gamma (IFN-γ), thereby inhibiting PD-L1 expression caused by the interaction of NK92-MI cells/PBMCs and HCC cells. Collectively, we are the first to demonstrate that BBR plays an immunomodulatory role by enhancing the cytotoxic effect of NK cells and inhibiting tumor immune escape by reducing the expression of PD-L1. Our study provides a theoretical basis for the clinical application of BBR combined with NK cells in the treatment of HCC.